The present invention relates to a method and a device for registering the outer characteristics of a vehicle in a road toll unit, wherein registration of the number plate, or other identification characteristic, of the vehicle may be carried out.
At automatic road toll units for a free traffic flow, it is assumed that the majority of vehicles passing are provided with a receiver-transmitter unit for radio waves such as a transponder. The road toll unit comprises an arrangement, by which communication over the radio waves may take place with passing vehicles. This arrangement comprises a transmitter and a receiver for the radio waves, by means of which equipment payment and debiting operations may be carried out for the passing vehicles, which are provided with the above-mentioned transponder. For this technology, reference is made, for example, to U.S. Pat. No. 4,075,632 and U.S. Pat. No. 4,242,661.
However, it may occur that the toll unit is passed by vehicles which do not have the correct payment equipment. For identification of such vehicles, if they attempt to pass the toll unit without making payment in any way, the toll unit is provided with camera devices for image registration of the number plates of such vehicles to enable tracing and subsequent charging.
In case of a large traffic volume in free formation, the respective vehicle will be able to move a certain distance between the time where a detection is carried out whether the vehicle is equipped to carry out a correct payment operation or not, and the time of recording the number plate.
During this movement of the vehicle, a division must be maintained between vehicles which are to be traced and subsequently charged, and vehicles for which payment has been secured. This requires that the toll arrangement is provided with equipment for registering the successive forward movement of the vehicle, such that it is ensured that an image is secured for the correct vehicle, that is, the vehicle for which an unsatisfactory payment status has been established in the road toll unit. This positioning check-up shall be capable of being carried out while several vehicles are moving in a free flow with possible lane-changing during the passage through the road toll unit. The check of the payment status shall be capable of being carried out at full speed of the vehicles, which leaves very little time for this operation.
From WO 94/28377 (Jonsson, Isaksson), an arrangement for registering the movement of the vehicles in the road toll unit is known. For this purpose, video cameras placed over the roadway are used, the position and successive movement of the respective vehicle being registered on the image plane of these cameras. In an image processing computer, a contour of the vehicle is connected to its identity in an image processing operation, and via the movement of this contour in the image plane in the camera, the movement of the vehicle can be successively registered. In the image processing operation, the position for the recording area is programmed to the camera which was used for imaging the number plate. When the vehicle is situated at this imaging point, exposure of the number plate may be performed by activating the imaging camera. The vehicle, the movement of which is being followed, has been identified, after entering the road toll unit, with regard to its payment status, such that for those vehicles which have an unsatisfactory payment status, an image may be presented.
The magnitude of the fee, with which vehicles passing the road toll unit is to be debited, is generally dependent on the type and size of the vehicle. For example, a single private car is charged a lower fee than a private car to which a trailer has been coupled, lorries are charged a still higher fee and, in addition, a surcharge if they have a trailer coupled to them, etc. The number of wheel axles may also be determining for the fee. In the normal case, it may be expected that the factors determining the size of the fee are clear from the radio message from the vehicle. However, experience shows that correct information is not always given. In such vehicles for which, because of an incorrectly effected payment operation, an image is to be taken, it may occur that the correct vehicle type cannot be obtained through the number plate, or that a check-up via the number plate becomes too complicated.
To ensure that a correct fee can always be debited, there is therefore a need to be able to register such external vehicle characteristics, as are of importance for the calculation of the fee, during the passage without disturbing the free flow. In this context, it is desirable to have a possibility, on the one hand, of determining the type of vehicle combinations which are being imaged because of an unsatisfactory payment status, and, on the other hand, of checking that the information which is obtained via radio communication from the vehicle equipment is correct.
The invention is based on the realization that the above-mentioned arrangement comprising video recording of the movement of the vehicle may be extended to provide an indication of the type of the vehicle and the composition of passing vehicles. During the payment operation, this indication may then be used to establish these data for the vehicles, the number plates or corresponding characteristics of which have been imaged for tracing and for checking whether these correspond to the information which has been communicated from the vehicle equipment.
In one embodiment of the invention, the indication of the type of vehicle, which may be obtained through the video recording, is supplemented by detection of the number of vehicle axles by means of sensors in the roadway. The reason for this is that the number of wheel axles is an often used means of determining the toll fee. If the video image is taken from above and down towards the roadway, the number of wheel axles may be difficult to read only from the image.
One important condition of the invention is that a system for following the position is used, which provides an unassailable connection of the image recording of the external shape of the vehicle and, where applicable, the registration of the number of vehicle axles with the registration of the identity of the vehicle, such as by means of an image of the number plate thereof. In this connection, the prior art disclosed in the above-mentioned WO94/28377 is preferably applied.